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The Torch of Death [was: Reviving Li-Ion cells?]

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Dr. Shark

Thu Jan 25 2007, 01:03PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

I've got two brocken battery packs from my iBook, which do not charge in the iBook anymore. Now I just took one apart and measured the individual cell voltage to be 0.05V. I suppose that this is usually considered a write-off - Battery University here

has a lot of info on that. Aparently copper filaments can form and short-circuit the cell, but anyway before I throw the cells away I though I might try if they still hold a charge.
I am sure somebody in the community here has done a similar thing before, so what are the chances of the cells working again? If I don't get any replies I'll just keep charging and the report back - in case my flat does not burn down that is

REPLY to myself (but not a double post):
Seems to work for some of the cells, others appear to be completely dead. Well, presumably the safety circuit in the battery pack shut it down for a reason, so very likely some of the cells just blew during normal use. Strange...

Anyway, THIS is what the cells are intended for: Since it can be kind of dark during winter in Finland, I decided that I need a manly flashligh. Therefore I aquired a HID (aka Xenon) Car headlight from eBay, and of course the electronic ballast /starting circuit required to run it. I acutally did all that a year ago, but I just realized it is winter again, so I started putting it together:

The picture just shows a couple of mockups, powered by a lab PSU since the Li-cells are not yet charged. I also need to do some more perspex work, a hole for a power switch and a handle.
The reflector is just the top of a pop bottle that happened to fit in my 100mm perspex pipe, covered with Al foil. Considering the shape of a bottle is not exaclty optimized to collimate light, I am quite happy with the focus of the light-beam.
Oh, this is a 35W HID bulb, which is about as bright as 100 to 150W of Halogen power. I estimate the converter to be about 70% efficient, consuming about 50W input power. That would mean I get about one hour of light from the 4400mAh cells, not bad considering the blinding brightness

Dr. Slack

Fri Jan 26 2007, 08:07AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

My manly flashlight is only a 55w halogen car fog lamp, running off my 12v drill NiCads, <envy> HID is definitely the way to go for more power </envy>. How much did you pay for it?

Steve Conner

Fri Jan 26 2007, 10:07AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Awesome! Now that is what I call a "manly" flashlight. I made a 10w halogen headlight for my bike when commuting in winter, and I thought it was plenty bright enough, a 35W HID would be insane :D

About the shorted Li-Ion cells, I don't believe they are recoverable. In the past, I have dismantled some Li-Ion laptop packs that the charger refused to deal with, and found that only one of the cells was shorted like that, and the others were usable. I saved the usable ones to experiment with, but I ended up destroying them by wrong charging. None of them exploded, though.

I looked at fancy batteries for my system, but ended up using those cheap 6V SLA batteries that are sold for kids' electric scooters and the like. They cost about Â£5, and the last one I bought worked for several years before it wouldn't hold charge any more.

Marko

Fri Jan 26 2007, 12:13PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Yup. Lithiums tend to simply fade away with time and there's nothing you can do to help them. They lose 10-20% of capacity per year even when not in use; sometimes they get shorted, or deep discharged (wich can be repaired, but is rare considering practically all stuf powered by lion's have their own regulator and UVLO.

Deep discharge is fixed by long charging, may take day or two. But it's also a very good way to torch the batteries, as steve probably did :/

Bjørn

Fri Jan 26 2007, 12:45PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Lithium-ion batteries stored with a partial charge and in cool temperatures can lose down to 2% capacity a year. Full charge and high temperatures like they would experience in some laptops would reduce the capacity with 30-40% a year.

Steve Conner

Fri Jan 26 2007, 02:19PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I heard that what kills laptop batteries early is leaving them fully charged all the time, as most people do when they operate the laptop off the AC adapter all the time with the batteries in.

Most modern laptops run scarily hot too, and get even hotter running off AC, so in the light of what Bjoern said, I guess the smart thing to do is to take the battery out if you're using the laptop with AC power for a long time, so it doesn't sit there hot and fully charged for hours on end.

I was recently messing around with a Toshiba Qosmio laptop that had not one, but two big heatpipe coolers with fans- one for the CPU and one for the GPU. It was faulty, and I think the GPU had in fact overheated and died after a long session watching DVDs on the AC adaptor. It just seems wrong to have a battery operated appliance with that much heat dissipation

Electroholic

Fri Jan 26 2007, 05:17PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

why would the laptop itself run hotter using ac?
if you are talking about the adapter i would understand.

BTW is the GPU a BGA?
sometimes the thermo expansion will kill it.
I have heard of ppl fixing G3 macbooks by blowtorching the GPUs.

...

Fri Jan 26 2007, 07:00PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

My laptop runs hotter when it is plugged in since F@H only runs on ac power

Sweet flashlight! I currently use a little head mounted one that runs off 3 AAA nicad batteries and has a luxeon LED in it. I get about 1hr of runtime on medium brightness, it weighs about 40g (great for those 50 mile backpacks at 14491') and is plenty bright for anything I do

Well, and then I have my 50w 808nm laser diodes, but they don't work too great as a flashlight (with the whole being invisable, and the 130lb power supply needed to run it)

BTW, when I read the title I thought that you had pushed the cells a little too hard and had one exploide on you...

Bjørn

Fri Jan 26 2007, 09:07PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

why would the laptop itself run hotter using ac?

It is not unusual that the CPU and other components enter an aggressive power saving mode when running on batteries. That means they run a significantly cooler with slightly reduced performance.

My laptop hardly ever starts the fan when running on batteries but on AC power it is running hot even when it is idle.

Dr. Shark

Sun Jan 28 2007, 03:47PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

OMG where is this board going, moderatos posting OT...

It't certainly true that LiIons degrade fairly rapidly, I think two years is a reasonalbe estimate for the average lifetime. People who really care about their laptops supposedly store the battery away from the computer and only put it in when they really need it...

Anyway, I think there was more wrong with my batteries than simple aging. One of them seems to have a short circuit of sorts, which I guess is a reasonable excuse for a battery to fail. Two others however, appered to be open circuit at first. I started ripping them apart to see if there was any lithium inside, and and with the top termial removed both cells sprang to life again! They even appeard to be fully charged, with a terminal voltage of 4.2V or so. The only reasonble explanation I can come up with is that not only the battery pack has saftey fuses, but the individual cells also do. The one cells shortening probably caused the other two around it to blow their fuses.

Well, project is canceled anyway since I only have three "working" batterys now and they dont seem to be able to drive the HID lamp properly.
I have some NiMHs that I could use, but I would have to spot-weld tabs to the cells, which would require spotwelding skills that I dont have. Doh.

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